Interconnection and/or repair of circuits on a substrate is commonly required in the manufacture of electronic components such as integrated circuits, integrated circuit modules, optoelectronic modules, and liquid crystal displays ("LCDs"). Open defects may occur during manufacturing or engineering changes may be desired. To repair these defects or make changes, it is generally desired to interconnect separated circuit lines across an open region of the substrate. This can be accomplished on opaque substrates by depositing a thin metal line on the substrate to connect the separated circuit lines.
In laser-induced chemical vapor deposition ("LCVD"), a focused laser is utilized to heat the surface of an opaque substrate at an open region between two separated circuit lines in the presence of a gaseous reactive compound. The focused laser beam is absorbed by the opaque substrate to cause localized heating of the substrate. The gaseous reactive compound such as an organometallic compound, adsorbed at the laser heated surface is pyrolyzed to metal and volatile reaction products. A line of the metal is plated onto the locally heated substrate as a thin film to interconnect the separated circuit lines. Baum et al., U.S. Pat. No. 4,880,959 discloses a process where a thin film circuit is repaired by LCVD with localized heating of an opaque substrate.
However, LCVD repair of thin film circuits on LCDs is more difficult. Because the substrate is transparent to the laser beam, there is no localized heating of the substrate by the focused laser beam to cause the pyrolytic deposition of metal on the substrate. Oprysko et al. U.S. Pat. No. 4,543,270 discloses a process for repairing defects on a transparent photomask. The first step of their process involves illuminating the entire surface of the substrate with ultraviolet light to cause dissociation of a gaseous organometallic precursor of trimethyl aluminum or hexacarbonyl tungsten and the formation of a nucleation layer of the metal-containing deposit on the substrate. The laser beam is then focused onto a localized region of the nucleated surface of the substrate to cause pyrolytic decomposition of the organometallic compound and deposition of the metal on the substrate. This process is generally unsuitable for circuit repair because the resulting metal containing lines have low electrical conductivity due to carbon/oxygen incorporation into the metal. Oprysko also separately suggests nucleation of the substrate adjacent to a metal pattern heated by a laser beam with subsequent metal containing deposit on that nucleated substrate.
However, there still is a need in the art for a method to connect spaced-apart electrical circuit lines disposed on a transparent substrate.
It is, therefore, an object of the present invention to provide a method for connecting spaced-apart circuit lines disposed on a transparent substrate.
Other objects and advantages will become apparent from the following disclosure.